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(No Model.)

a O. F. BRACKETT.v

ELEGTRO MAGNETIG DYNAMOMETER.

No. 287,800. Patented Nov. 6, 1883.

1- UNITEn-ST r PATENT CYRUS F. BRAOKETT, OF PRINCETON, NEW JERSEY.

ELECTRO-MAGN'E'TIQI DYNAMOMETERL SPECIFICATIONforming part of Letters Patent 15rd. 287,800, dated November 6, 188 3, Application filed June 20,1883. (No model) i I To aZZ' whom it may concern.-

Be itknown that I, OYRUs F. BRAOKETT, a" citizen of the United States, residing at Princeton, in the county of Mercer and State of New Jersey, have invented a certain new and use-' 'ful Electro-Magnetic Dynamometer, of which the following is a specification. The nature of this invention and the proper methods of applying it will be easily under-v stood from the following exposition, reference being had to, the accompanying drawings, and to the letters affixed thereto. a

When the armature of a dynamo-machine is made to revolve, the circuit being closed, there is developed between the armature and the fieldmagnets a mechanical couple, which tends to cause the field-magnets to revolve in the same direction with the armature. If the field-magnets were balanced without friction,

. other.

and were otherwise unobstructed, so as to be free to revolve, they would do so with increasing velocity, till at length they would perform their revolutions in the same time with the armature, when the current would be reduced to zero. If, instead of permitting such revolution, we were to apply another couple tending to make the field-magnets revolve in the opposite direction, and wereto make its value equal to that of the couple set up by the current, the field-magnets would remain at rest; We could always know the value of the couple thus applied, since it might be applied asa known pressure at a definite point on aleverarm. We should then, in addition, only need to know the velocity of the armature in order to determine the energy sought. How these principles are embodied in my invention I now proceed to point; out. i

Figures I and 2 represent a dynamo-machine to which my invention is applied standing in two positions at right angles to one an- The field-magnets A are supported on two uprights,S,which are fixedto thebase O. The support is effected by means of a rigid bar, G, through whose ends pass the rods K. One of these rods terminates in a knife-edge and the other in a point, both of hard steel. These t )lIIliIlEttlOllS rest, the onein a groove, the other in a cone-shaped cavity, also both of hard steel. This arrangement is designed to'prevent displacements of the magnets from acci- .uated in equal parts, reference being had to some convenientunit of length. The zeropoints of the graduation lie in the axis of revolution of the armature. The lever-arms are designed to carry sliding weights of known value, to be employed in producing the couple which acts in opposition to that set up by the current, as before pointed out; or springs may be used instead, of weights. The whole magnet system, together with its supporting-bar and attachments, is so balanced that its center of gravity is very slightly below the line passing through the knife-edge and point on which it rests, as in the common balance. I The are through which'the lever-arms can turn is kept within limits-convenient for observation by means of any convenient stops, which need not be specified. f

' Suppose the machine, in the position shown in Fig. 1, to be set in motion, the circuit being closed, and the revolution of the armature- 'being in the direction. of the hands of a watch, the field-magnets, being free to turn through a small are, will be displaced from their position'of horizontal equilibrium, so

that the arm X will beraised and the arm X y will be depressed. Asliding weight, W, (not shown,) is to be placed on the arm X and moved, if necessary, tillthe couple thus applied is equal to that developed by the action of the machine. The energy expended during one revolution of the armature is nowfound 9 5 by taking the product of the'number of units in the circumference of the circle, whose ra-- dius is determined by the position of. the weight on the lever-arm, by the number of units contained in the weight. This product multiplied by the number of revolutions per minute gives the energy expended per minute; or, if W be the weight in pounds, a the length of the effective lever-arm in feet, and

n the number of revolutions in a minute, we may express the result bya formula, thus: Ft. lbs. per min.:\V 2na a. The velocity of revolution is ascertained by means of a counter, which is applied, in the usual way, at the center H. In a precisely similar way the mechanical energy developed by the machine when used as a motor is ascertained, reference being had to the direction of revolution which the field-magnets tend to assume.

The application of the main principle of the invention herein set forth is not limited to the special form of machine shown in the accompanying drawings, but it may be made as well to all machines which produce a current of electricity by the revolution of an armature in a magnetic field, or, conversely, by the revolution of a magnetic field about an armature.

Any convenient form of support for the field-magnets which will permit the requisite freedom of motion may be adopted instead of the one herein described.

This invention may be employed also in measuring the energy delivered by any revolving shaft in the performance of its duty as a prime motor. For this purpose an armature is secured to the shaft whose energy at a given speedsay that maintained when doing its usual dutyis to be measured, and suitable field-magnets are properly placed and supported, so as to act in accordance with the principles already set forth. The usual work is now thrown off, and the circuit of the armature and magnets is closed through a resistance which can be varied at pleasure. Now, the current produced, and consequently the amount of work done upon the electro-magnetic system, will depend on the resistance of the circuit. varied until the speed of the shaft is made equal to the given speed. The energy delivered to the electro-magnetic dynamometer is then computed as heretofore described.

It is evident that by employing a suitable means of determining the value of the current produced with different speeds and with different resistances in the circuit a table may be constructed which shall contain these factors of current, speed, and resistance, together with the energy corresponding, which can be found as before pointed out. The advantage of such a table would consist in its ready application when once prepared in cases where for any reason it is desired to keep the fieldmagnets fixed, as is the case with ordinary forms of dynamo and magneto machines.

Having now fully described my invention and pointed out its applications, what I desire to claim and secure by Letters Patent is 1. The process of measuring themechanical energy of a revolving shaft, which consists in measuring the mechanical couple set up between the elements of a magneto-electric or This resistance is therefore to be an electromagnetic system, where one of such elements revolves with the energy to be measured and the other, is held fixed, substantially as shown and described.

2. The process of measuring the energy of a revolving shaft, which consists in measuring the mechanical couple set up between the elements of a magneto-electric or eleetro-magnetic system, where one of such elements revolves with the energy to be measured and the other is held fixed, by measuring the couple necessary to hold such other element fixed, substantially as shown and described.

3. The process of measuring the energy expended on a dynamo or magneto machine when used as a generator, or derived from such machines when used as motors; which consists in measuring the mechanical couple set up between the revolving element and the stationary element of such machine, substantially as shown and described.

4. The process of measuring the energy expended on a dynamo or magneto machine when used as a generator, or given out by such a machine when used as a motor, which consists in measuring the mechanical couple set up between the revolving element and thestationary element of such machine, by measuring the couple required to hold such second element stationary, substantially as shown and described.

. 5. In an electro-generative or an electromotive system, the combination of a revolving and a rocking element with means, as described, of measuring the mechanical couple set up between the two elements, substantially as and for the purposes set forth.

6. In an electro generative or an electromotive system, the combination of a revolving element and a stationary element with means, as described, of measuring the force required to hold the said second element stationary, substantially as and for the purposes set forth.

7. In an electro-generative or an electromotive system, the combination of a revolving element with a rocking element having lever-arms andweights adjustable on the same, whereby the said rocking element is balanced, substantially as and for the purposes set forth.

8. In an electro-generative or an electromotive system, the combination of a revolving armature with field-magnets mounted 011 knife-edge and point, as described, and having lever-arms with weights adj ustable there on, whereby the mechanical couple set up between the armature and the field-magnets may be measured, substantially as and for the purposes set forth.

CYRUS F. BRACKETT. Vitnesses:

WM. HARRIS, EDWIN C. OSBORN. 

